Field of the Invention
The present invention is related to a microscope objective and particularly to a dry microscope objective.
Description of the Related Art
In the field of biology, inverted microscopes are often used for observing a sample such as a cultured cell. Observation magnifications from around 20× through 60× are often used because a plurality of cultured cells are often observed at a time.
In an inverted microscope, light from the sample enters the objective via a sample container or a slide glass. Examples of a sample container include a glass petri dish, a plastic dish, etc. Lengths of sample containers range from approximately 0.15 mm, which is similar to that of a cover glass, to approximately 1 mm.
This has created demands for a microscope objective that has a mechanism for correcting aberrations caused by variation in thickness of a slide glass, a cover glass, a petri dish, a dish, etc. (these elements will collectively be referred to as a sample holding member hereinafter) that is disposed between the sample and the objective. Such an objective is disclosed by for example Japanese Laid-open Patent Publication No. 2005-352021. Example 1 of Japanese Laid-open Patent Publication No. 2005-352021 discloses an objective that can correct aberrations in a cover glass with a thickness from approximately 0 mm through 2 mm, and can also suppress excellently aberrations including a chromatic aberration, field curvature, etc.